A temperature sensing element includes a thermistor composed of Si-base ceramics and a pair of metal electrodes bonded onto the surfaces of the thermistor. The metal electrodes contain Cr and a metal element α having a Si diffusion coefficient higher than that of Cr. A diffusion layer is formed in a bonding interface between the thermistor and each metal electrode, the diffusion layer including a silicide of the metal element α in a crystal grain boundary of the Si-base ceramics. A temperature sensor including the diffusion layers is provided. Owing to the diffusion layers, the temperature sensor ensures heat resistance and bonding reliability and enables temperature detection with high accuracy in a temperature range, in particular, of from −50° C. to 1050° C.